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For an ordinary file, call os.path.getsize(path) or read Path(path).stat().st_size. Both return the size in bytes. To display KB or MB, divide that byte count by the decimal or binary unit you intend to use.
Get a file size in bytes
The simplest option is os.path.getsize():
import os
size_bytes = os.path.getsize("report.pdf")
print(size_bytes)It returns the size in bytes and accepts path-like objects in Python 3.6 and later. The call raises OSError if the path does not exist or cannot be accessed. See the Python 3.14 os.path documentation.
If your code uses pathlib, read st_size from the path’s stat result:
from pathlib import Path
size_bytes = Path("report.pdf").stat().st_size
print(size_bytes)For an ordinary file, st_size is its size in bytes. Path.stat() returns a broader status result, which is useful if you need other file metadata too. See the Python 3.14 pathlib documentation.
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Convert bytes to KB, MB, KiB, or MiB
The APIs return bytes; converting to larger units is arithmetic for display. Decimal units divide by powers of 1,000. Binary units divide by powers of 1,024. For clarity, label binary results KiB and MiB rather than KB and MB.
size_kb = size_bytes / 1_000
size_mb = size_bytes / 1_000_000
size_kib = size_bytes / 1_024
size_mib = size_bytes / (1_024 ** 2)For example, to display a file size in binary mebibytes to two decimal places:
from pathlib import Path
size_bytes = Path("report.pdf").stat().st_size
size_mib = size_bytes / (1024 * 1024)
print(f"{size_mib:.2f} MiB")Some interfaces label binary values KB and MB. If you are matching one, use its convention deliberately: dividing by 1,024 and 1,048,576 produces KiB and MiB, even if the interface calls them KB and MB.
Choose between os.path.getsize() and Path.stat().st_size
| Option | Use it when | What you get |
|---|---|---|
os.path.getsize(path) |
You want a direct byte-count call or your code already uses os.path. |
A size in bytes. |
Path(path).stat().st_size |
Your code already uses pathlib, or you may also need other stat information. |
A size in bytes, read from the stat result. |
Both are standard-library options; choose based on the style and information your code needs. Neither call locks the file. The value is a filesystem status snapshot and can become outdated if the file changes afterward.
Handle missing or inaccessible paths
When a lookup can fail, catch OSError rather than treating the error as a zero-byte file:
from pathlib import Path
try:
size_bytes = Path("report.pdf").stat().st_size
except OSError as exc:
print(f"Could not read file size: {exc}")
else:
print(f"{size_bytes} bytes")This handles failures such as a missing path or insufficient access. Decide in your application whether to report the error, retry, or take another action.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What happens with symbolic links and special files?
Normal os.path.getsize() and Path.stat() calls follow symbolic links, so they report the target’s size. To inspect the link itself instead, use Path(path).lstat().st_size. The Path.stat(follow_symlinks=False) option is documented as available from Python 3.10. See the Python 3.14 os.stat documentation.
A symbolic link’s own reported size is the length of its stored pathname, without a terminating null byte. For special files, st_size may not describe ordinary file contents: on many Unix systems, a FIFO or socket can report the bytes waiting to be read, and behavior for other special files varies by implementation. These examples are intended for ordinary files; see the Python 3.14 stat documentation for details.
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